Did Newman on the 'Seinfeld' show have a first name?

No.

Newman is a secondary character on the television show Seinfeld. He is played by Wayne Knight. Like fellow Seinfeld character Cosmo Kramer, Newman is addressed by last name, a fact Newman revealed in episode 44, The Ticket. Unlike Kramer, Newman's first name is never mentioned, even though in one of the episodes after Newman runs out of a house and is getting shot at, a woman shouts after him: "I'll never forget you Norman" which is probably a joke about her not knowing his name, although this cannot be said with certainty. Newman is considered by some to be the villain in the series.
http://www.answers.com/topic/newman-seinfeld


[Added reference - McG]